Winter Weather Across America

Source: The Federal Emergency Management Agency (FEMA)

From the Mid-Atlantic Coast to New England

The classic storm in these states is called a Nor'easter. A low-pressure area off the Carolina coast strengthens and moves north. Wind-driven waves batter the coast from Virginia to Maine, causing flooding and severe beach erosion. The storm taps the Atlantic's moisture-supply and dumps heavy snow over the region. The snow and wind may combine into blizzard conditions and form deep drifts paralyzing some areas. Ice storms are also a problem. Mountains, such as the Appalachians, act as a barrier to cold air trapping it in the valleys and nearby low elevations. Warm air and moisture moves over the cold, trapped air. Rain falls from the warm layer onto a cold surface below becoming ice.

Along the Gulf Coast and Southeast

This region is usually doesn't get much snow, ice or freezing temperatures. Once in a while, though, cold air penetrates south across Texas and Florida, into the Gulf of Mexico. Temperatures fall below freezing, killing tender vegetation, such as flowering plants and the citrus fruit crop. Wet snow and ice accumulate on trees with leaves, causing the branches to snap under the load. Motorists are unsure how to drive on slick roads and there can be a lot of traffic accidents. Some buildings are poorly insulated or lack heat altogether so it can be cold inside! Cities may not have snow removal equipment or treatments, such as sand or salt, for icy roads.

In the Midwest and Plains

Storms tend to develop over southeast Colorado. These storms move east or northeast and use both the southward plunge of cold air from Canada and the northward flow of moisture from the Gulf of Mexico to produce heavy snow and sometimes blizzard conditions. Other storms affecting the Midwest and Plains move southeast. Arctic air is drawn from the north and moves south across the Plains and Great Lakes. Wind and cold sometimes combines to cause wind chill temperatures as low as 70°F below zero! The wind crosses the lakes, tapping its moisture and forming snow squalls and narrow heavy snow bands. This is called “lake-effect snow.”

From the Rockies to the West Coast

Strong storms crossing the North Pacific sometimes slam into the coast from California to Washington. The vast Pacific provides an unlimited source of moisture for the storm. If it's cold enough, snow falls over Washington and Oregon and sometimes even in California. As the moisture rises into the mountains, heavy snow closes the mountain passes and can cause avalanches. The cold air from the north has to filter through mountain canyons into the basins and valleys to the south. If the cold air is deep enough, it can spill over the mountain ridge. As the air funnels through canyons and over ridges, wind speeds can reach 100 mph, damaging roofs and taking down power and telephone lines. Combining these winds with snow results in a blizzard.

In Alaska

Wind-driven waves from intense storms crossing the Bering Sea produce coastal flooding and can drive large chunks of sea ice inland, destroying buildings near the shore. High winds, especially across Alaska's Arctic coast, can combine with loose snow to produce a blinding blizzard and wind chill temperatures to 90°F below zero! Extreme cold (-40°F to -60°F) and ice fog may last for as long as a week at a time. Heavy snow can impact the interior of the state, especially along the southern coast. The snow accumulates through the winter months and in the mountains, it builds glaciers. The heavy snow accumulations can cause avalanches or collapse roofs of buildings. A quick thaw means certain flooding. Ice jams on rivers can also cause substantial flooding.